print_vma_addr possible deadlock (was Re: Jeste jeden bug)

From: Jiri Kosina
Date: Wed Feb 13 2008 - 11:59:33 EST


[ sorry for forgetting to change subject properly :) ]

On Wed, 13 Feb 2008, Jiri Kosina wrote:

> [ the original mail was sent by Zdenek to me offlist ]
>
> On Wed, 13 Feb 2008, Zdenek Kabelac wrote:
>
> > [ 68.379022] gnome-settings-[2941] trap int3 ip:3d2c840f34
> > sp:7fff36f5d100 error:0<3>BUG: sleeping function called from invalid
> > context at kernel/rwsem.c:21
> > [ 68.379039] in_atomic():1, irqs_disabled():0
> > [ 68.379044] no locks held by gnome-settings-/2941.
> > [ 68.379050] Pid: 2941, comm: gnome-settings- Not tainted 2.6.25-rc1 #30
> > [ 68.379054]
> > [ 68.379056] Call Trace:
> > [ 68.379061] <#DB> [<ffffffff81064883>] ? __debug_show_held_locks+0x13/0x30
> > [ 68.379109] [<ffffffff81036765>] __might_sleep+0xe5/0x110
> > [ 68.379123] [<ffffffff812f2240>] down_read+0x20/0x70
> > [ 68.379137] [<ffffffff8109cdca>] print_vma_addr+0x3a/0x110
> > [ 68.379152] [<ffffffff8100f435>] do_trap+0xf5/0x170
> > [ 68.379168] [<ffffffff8100f52b>] do_int3+0x7b/0xe0
> > [ 68.379180] [<ffffffff812f4a6f>] int3+0x9f/0xd0
> > [ 68.379203] <<EOE>>
> > [ 68.379229] in libglib-2.0.so.0.1505.0[3d2c800000+dc000]
>
> Andi,
>
> in commit 03252919 you introduced print_vma_addr(), but this funcion for
> obvious reasons takes mmap_sem, so it is not safe to call it from atomic
> context (i.e. do_trap(), for example), which is behavior your patch
> introduced.
>
>
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